Hydrogen-Etched TiO2−x as Efficient Support of Gold Catalysts for Water–Gas Shift Reaction

Li Song,Yuting Zhang,Lei Li,Qi Su,Zhufeng Lu

doi:10.3390/catal8010026

Abstract

Hydrogen-etching technology was used to prepare TiO2−x nanoribbons with abundant stable surface oxygen vacancies. Compared with traditional Au-TiO2, gold supported on hydrogen-etched TiO2−x nanoribbons had been proven to be efficient and stable water–gas shift (WGS) catalysts. The disorder layer and abundant stable surface oxygen vacancies of hydrogen-etched TiO2−x nanoribbons lead to higher microstrain and more metallic Au0 species, respectively, which all facilitate the improvement of WGS catalytic activities. Furthermore, we successfully correlated the WGS thermocatalytic activities with their optoelectronic properties, and then tried to understand WGS pathways from the view of electron flow process. Hereinto, the narrowed forbidden band gap leads to the decreased Ohmic barrier, which enhances the transmission efficiency of “hot-electron flow”. Meanwhile, the abundant surface oxygen vacancies are considered as electron traps, thus promoting the flow of “hot-electron” and reduction reaction of H2O. As a result, the WGS catalytic activity was enhanced. The concept involved hydrogen-etching technology leading to abundant surface oxygen vacancies can be attempted on other supported catalysts for WGS reaction or other thermocatalytic reactions.

Highlights

Hydrogen is a promising clean, efficient and sustainable energy source and can be a suitable candidate to reduce the dependence on fossil fuels
water–gas shift (WGS) catalytic activities compared with the white TiO2 nanoribbon (TiO2 -N) support
The results indicate that that structural disorder was rather responsible atmosphere resulted in the surface oxygen vacancies due to the reduction of the surface oxygen for the broadening of the bands observed in black TiO2 [51]

Summary

Introduction

Hydrogen is a promising clean, efficient and sustainable energy source and can be a suitable candidate to reduce the dependence on fossil fuels. In this sense, the water–gas shift (WGS) reaction (CO + H2 O = CO2 + H2 ) is crucial in industrially producing pure hydrogen, because the reaction provides hydrogen generation and CO cleanup. To develop new and more efficient WGS catalysts, supported catalysts have been believed to be good candidate. Au-TiO2 catalysts have been given considerable attentions for WGS activities, due to the high activity and low side reactions of dispersed Au [38], and some advantages of TiO2 supports (e.g., low price, easy preparation, adjustable properties and strong interaction with active metal)

Methods

Results

Discussion

Conclusion